I was coming in here to post the same thing. It's the one aspect of combat that I just can't get right 100% of the time, and this AR challenge where you have to do 2 of them, kill the medic last, and don't take damage is taking me forever because the Fear Takedown prompt is so random.
I just went for a double takedown twice for that, since it counts as a fear takedown now.
But I agree, I think it's a pretty weak inclusion even if it looks cool. It also makes it damn easy to wreck in the predator maps when you can take on groups like this. I like the wrinkle Medics and the Detective Mode tracker adds to predator segments though, even if the disruptor is super powerful.